(a) Field of the Invention
The present invention relates to a frequency reconfiguring antenna array technique.
This work was supported by the IT R&D program of MIC/IITA [2007-F-041-01, Intelligent Antenna Technology Development].
(b) Description of the Related Art
A frequency reconfiguration antenna can vary antenna parameters such as frequency, polarization, and pattern by electrical or mechanical control, and a frequency reconfiguration antenna is reconfigured to be operable in at least two different frequency bandwidths. In this instance, when configuring the frequency reconfiguration antenna element as a frequency reconfiguration array antenna, the interval between elements is fixed with reference to a single frequency, in general, the center frequency of the intermediate bandwidth in the entire reconfiguration bandwidth.
In general, when a random frequency reconfiguration antenna is arranged, a radiation pattern of an array antenna is expressed in Equation 1.Ptotal(ω)=Pelement(ω)×AF(ω)  (Equation 1)
Here, Ptotal(w) is a radiation pattern of the entire array antenna, Pelement(w) is a radiation pattern of the frequency reconfiguration antenna element which is a single element, and AF(w) is an array factor. The array factor is determined by a physical gap between frequency reconfiguration antenna elements, intensity ratio of signals supplied to the respective antenna elements, and phase difference. The radiation pattern and the array factor of the frequency reconfiguration antenna element are variable by the frequency, and hence the radiation pattern of the entire frequency reconfiguration array antenna is also variable by the frequency.
Therefore, when (N×M) antenna elements are arrayed and the amplitudes and phase of the signals supplied to the respective antenna elements are the same, the amplitude ratio and the phase difference between the radiation pattern of the antenna element and the supplied signal are determined, and hence the radiation pattern of the frequency reconfiguration array antenna is variable according to the physical distance between the antenna elements.
The array gain of the frequency reconfiguration array antenna is varied depending on the physical distance between the antenna elements, and when the distance is fixed with reference to a frequency bandwidth, the array gain of the frequency reconfiguration array antenna in another frequency bandwidth is reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.